While most of those problems are "artistic" ones, many of them are quite hard, so I thought useful to give a (very rough) indication of their difficulty : some easy reference positions are not ranked, but for the others :
one means the problem can be solved (in a reasonable time, without moving stones) by a player around 1k (52 problems),
two
means a 5d level (57 problems),
three means a professional level (40 problems). And, of course, Dosetsu's problem, and 12 others, are ranked ...